Introgression and rapid species turnover in sympatric damselflies

<p>Abstract</p> <p>Background</p> <p>Studying contemporary hybridization increases our understanding of introgression, adaptation and, ultimately, speciation. The sister species <it>Ischnura elegans </it>and <it>I. graellsii </it>(Odonata: Coenagrionidae) are ecologically, morphologically and genetically similar and hybridize. Recently, <it>I. elegans </it>has colonized northern Spain, creating a broad sympatric region with <it>I. graellsii</it>. Here, we review the distribution of both species in Iberia and evaluate the degree of introgression of <it>I. graellsii </it>into <it>I. elegans </it>using six microsatellite markers (442 individuals from 26 populations) and five mitochondrial genes in sympatric and allopatric localities. Furthermore, we quantify the effect of hybridization on the frequencies of the genetically controlled colour polymorphism in females of both species.</p> <p>Results</p> <p>In a principal component analysis of the microsatellite data, the first two principal components summarised almost half (41%) of the total genetic variation. The first axis revealed a clear separation of <it>I. graellsii </it>and <it>I</it>. <it>elegans </it>populations, while the second axis separated <it>I. elegans </it>populations. Admixture analyses showed extensive hybridization and introgression in <it>I. elegans </it>populations, consistent with <it>I. elegans </it>backcrosses and occasional F₁-hybrids, suggesting hybridization is on-going. More specifically, approximately 58% of the 166 Spanish <it>I. elegans </it>individuals were assigned to the <it>I. elegans </it>backcross category, whereas not a single of those individuals was assigned to the backcross with <it>I. graellsii</it>. The mitochondrial genes held little genetic variation, and the most common haplotype was shared by the two species.</p> <p>Conclusions</p> <p>The results suggest rapid species turnover in sympatric regions in favour of <it>I. elegans</it>, corroborating previous findings that <it>I. graellsii </it>suffers a mating disadvantage in sympatry with <it>I. elegans</it>. Examination of morph frequency dynamics indicates that hybridization is likely to have important implications for the maintenance of multiple female morphs, in particular during the initial period of hybridization.</p

A de novo transcriptome of the Asian tiger mosquito, Aedes albopictus, to identify candidate transcripts for diapause preparation

<p>Abstract</p> <p>Background</p> <p>Many temperate insects survive the harsh conditions of winter by undergoing photoperiodic diapause, a pre-programmed developmental arrest initiated by short day lengths. Despite the well-established ecological significance of photoperiodic diapause, the molecular basis of this crucial adaptation remains largely unresolved. The Asian tiger mosquito, <it>Aedes albopictus </it>(Skuse), represents an outstanding emerging model to investigate the molecular basis of photoperiodic diapause in a well-defined ecological and evolutionary context. <it>Ae. albopictus </it>is a medically significant vector and is currently considered the most invasive mosquito in the world. Traits related to diapause appear to be important factors contributing to the rapid spread of this mosquito. To generate novel sequence information for this species, as well as to discover transcripts involved in diapause preparation, we sequenced the transcriptome of <it>Ae. albopictus </it>oocytes destined to become diapausing or non-diapausing pharate larvae.</p> <p>Results</p> <p>454 GS-FLX transcriptome sequencing yielded >1.1 million quality-filtered reads, which we assembled into 69,474 contigs (N50 = 1,009 bp). Our contig filtering approach, where we took advantage of strong sequence similarity to the fully sequenced genome of <it>Aedes aegypti</it>, as well as other reference organisms, resulted in 11,561 high-quality, conservative ESTs. Differential expression estimates based on normalized read counts revealed 57 genes with higher expression, and 257 with lower expression under diapause-inducing conditions. Analysis of expression by qPCR for 47 of these genes indicated a high correlation of expression levels between 454 sequence data and qPCR, but congruence of statistically significant differential expression was low. Seven genes identified as differentially expressed based on qPCR have putative functions that are consistent with the insect diapause syndrome; three genes have unknown function and represent novel candidates for the transcriptional basis of diapause.</p> <p>Conclusions</p> <p>Our transcriptome database provides a rich resource for the comparative genomics and functional genetics of <it>Ae. albopictus</it>, an invasive and medically important mosquito. Additionally, the identification of differentially expressed transcripts related to diapause enriches the limited knowledge base for the molecular basis of insect diapause, in particular for the preparatory stage. Finally, our analysis illustrates a useful approach that draws from a closely related reference genome to generate high-confidence ESTs in a non-model organism.</p

Seasonal Pattern of Batrachochytrium dendrobatidis Infection and Mortality in Lithobates areolatus: Affirmation of Vredenburg's “10,000 Zoospore Rule”

To fully comprehend chytridiomycosis, the amphibian disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), it is essential to understand how Bd affects amphibians throughout their remarkable range of life histories. Crawfish Frogs (Lithobates areolatus) are a typical North American pond-breeding species that forms explosive spring breeding aggregations in seasonal and semipermanent wetlands. But unlike most species, when not breeding Crawfish Frogs usually live singly—in nearly total isolation from conspecifics—and obligately in burrows dug by crayfish. Crayfish burrows penetrate the water table, and therefore offer Crawfish Frogs a second, permanent aquatic habitat when not breeding. Over the course of two years we sampled for the presence of Bd in Crawfish Frog adults. Sampling was conducted seasonally, as animals moved from post-winter emergence through breeding migrations, then back into upland burrow habitats. During our study, 53% of Crawfish Frog breeding adults tested positive for Bd in at least one sample; 27% entered breeding wetlands Bd positive; 46% exited wetlands Bd positive. Five emigrating Crawfish Frogs (12%) developed chytridiomycosis and died. In contrast, all 25 adult frogs sampled while occupying upland crayfish burrows during the summer tested Bd negative. One percent of postmetamorphic juveniles sampled were Bd positive. Zoospore equivalents/swab ranged from 0.8 to 24,436; five out of eight frogs with zoospore equivalents near or >10,000 are known to have died. In summary, Bd infection rates in Crawfish Frog populations ratchet up from near zero during the summer to over 25% following overwintering; rates then nearly double again during and just after breeding—when mortality occurs—before the infection wanes during the summer. Bd-negative postmetamorphic juveniles may not be exposed again to this pathogen until they take up residence in crayfish burrows, or until their first breeding, some years later

Scintillation light detection in the 6-m drift-length ProtoDUNE Dual Phase liquid argon TPC

DUNE is a dual-site experiment for long-baseline neutrino oscillation studies, neutrino astrophysics and nucleon decay searches. ProtoDUNE Dual Phase (DP) is a 6  ×  6  ×  6 m 3 liquid argon time-projection-chamber (LArTPC) that recorded cosmic-muon data at the CERN Neutrino Platform in 2019-2020 as a prototype of the DUNE Far Detector. Charged particles propagating through the LArTPC produce ionization and scintillation light. The scintillation light signal in these detectors can provide the trigger for non-beam events. In addition, it adds precise timing capabilities and improves the calorimetry measurements. In ProtoDUNE-DP, scintillation and electroluminescence light produced by cosmic muons in the LArTPC is collected by photomultiplier tubes placed up to 7 m away from the ionizing track. In this paper, the ProtoDUNE-DP photon detection system performance is evaluated with a particular focus on the different wavelength shifters, such as PEN and TPB, and the use of Xe-doped LAr, considering its future use in giant LArTPCs. The scintillation light production and propagation processes are analyzed and a comparison of simulation to data is performed, improving understanding of the liquid argon properties

Separation of track- and shower-like energy deposits in ProtoDUNE-SP using a convolutional neural network

Liquid argon time projection chamber detector technology provides high spatial and calorimetric resolutions on the charged particles traversing liquid argon. As a result, the technology has been used in a number of recent neutrino experiments, and is the technology of choice for the Deep Underground Neutrino Experiment (DUNE). In order to perform high precision measurements of neutrinos in the detector, final state particles need to be effectively identified, and their energy accurately reconstructed. This article proposes an algorithm based on a convolutional neural network to perform the classification of energy deposits and reconstructed particles as track-like or arising from electromagnetic cascades. Results from testing the algorithm on experimental data from ProtoDUNE-SP, a prototype of the DUNE far detector, are presented. The network identifies track- and shower-like particles, as well as Michel electrons, with high efficiency. The performance of the algorithm is consistent between experimental data and simulation

Separation of track- and shower-like energy deposits in ProtoDUNE-SP using a convolutional neural network

Liquid argon time projection chamber detector technology provides high spatial and calorimetric resolutions on the charged particles traversing liquid argon. As a result, the technology has been used in a number of recent neutrino experiments, and is the technology of choice for the Deep Underground Neutrino Experiment (DUNE). In order to perform high precision measurements of neutrinos in the detector, final state particles need to be effectively identified, and their energy accurately reconstructed. This article proposes an algorithm based on a convolutional neural network to perform the classification of energy deposits and reconstructed particles as track-like or arising from electromagnetic cascades. Results from testing the algorithm on data from ProtoDUNE-SP, a prototype of the DUNE far detector, are presented. The network identifies track- and shower-like particles, as well as Michel electrons, with high efficiency. The performance of the algorithm is consistent between data and simulation